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Abstract

The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 μW and 19 μW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission.

The light-in light-out curves of a representative cavity, using (a) the 980 nm pump and (b) the 780 nm pump laser. Fits from the rate equations, and linear fits to the above threshold behavior are also shown. (c) The power dependence of the cavity wavelength with 780 nm and 980 nm pump. The red-shift at high pump powers indicates structure heating, and it kicks off sooner if the above-GaAs bandgap laser (780nm) is employed, as expected. The inset shows the cavity intensity for larger pump powers, where the beginning of saturation is observed toward the end of both traces. (d) The power dependence of the cavity linewidth with 780 nm and 980 nm pump. The pump power (horizontal axis) is measured before the objective in all cases.

The thresholds of various nanobeam lasers obtained by linear fit to the above threshold behavior, using both the 780 nm and the 980 nm pump. Threshold pump powers are measured before the objective lens in all cases. The Qs of various cavities (all below threshold) are also shown.

The light-in light-out curve for the same cavity as in Fig. 3(a)–3(b), pumped with a pulsed 830 nm laser, and by a CW 830 nm laser. The emission from a portion of the PL spectrum not coupled to the cavity is also shown. Pump powers are measured in front of the objective.

(a) Spectra from a nanobeam cavity as it is tuned by the movement of a fiber taper in close proximity to the cavity. The free space spectrum without the fiber taper is shown as a reference, and taper movement in the y- and z-directions (shown in Fig. 1) tunes the cavity mode by over 7 nm. The spectra for the tuned cavity are scaled for clarity. (b) The lasing thresholds of one cavity pumped from free space (normal incidence) and through the fiber taper, with collection through the fiber taper in both cases. The fiber taper position is varied to tune the lasing wavelengths. A reference case without any fiber tapers is also shown as the data point with the shortest wavelength. The inset shows the geometry simulated by FDTD, as well as the ∣E∣2 field of the cavity mode in the presence of the fiber taper.